The following invention relates to stent-grafts which are utilized to support or replace a damaged body lumen, such as an artery. More particularly, this invention relates to vascular stent-grafts which can be implanted intraluminally or with direct surgical techniques and which provide a smooth continuous elongate tube structure for transport of bodily fluids through the damaged area.
Body lumens such as arteries can become damaged in a variety of different ways. For instance, diseases such as arteriosclerosis and aneurysms result in degeneration of the arterial wall. Depending on the type of damage to the artery and the extent of such damage, various different treatments can be used for these conditions. Where the damaged artery wall is still somewhat viable, a radially expandable stent can be implanted intraluminally and radially expanded at the site of damage to support the wall in the desired open position. Examples of such stents can be found in the Handbook of Coronary Stents, Second Edition. Stent-grafts are also described in journals such as the Journal of Endovascular Therapy (see for example issue 2000; 7) U.S. Pat. No. 6,042,606, incorporated herein by reference, also describes details of surgical stents utilizable to support a damaged artery wall or other body lumen.
When the artery wall is sufficiently deteriorated that it can no longer function properly, a graft can be placed within the damaged portion of the artery to support blood flow or other body fluid flow past the damaged area. While such grafts include a structural component to keep the graft in a desired location and/or shape, they are referred to as stent-grafts. Such stent-grafts can come in two varieties. First, the stent-graft can be placed intraluminally within the damaged portion of the artery with the damaged portion of the artery remaining in position but no longer being relied upon to support blood flow past the damaged area. Second, the stent-graft can directly be surgically implanted by removal of the damaged artery section and replacement with the stent-graft.
Such stent-grafts provide a number of basic functions. They include a solid film which is impervious to fluid flow therethrough so that it can contain blood or other bodily fluid flow within the lumen pathway. They include some structure for securely holding the stent-graft in position adjacent the damaged portion of the artery and to keep a desired shape for the stent-graft and exhibit sufficient structural strength to handle the fluid pressure and surrounding forces without failure.
Known prior art stent-grafts have included a separate fluid containment layer and a separate structural support layer. For instance, the World Medical Manufacturing Corporation of Sunrise, Fla. produces a stent-graft under the trademark TALENT that includes a Dacron fabric covering a radially expandable nickel-titanium support structure (see the Journal of Endovascular Therapy 2000; 7: 132-135, 133). Other known stent-grafts include the JOSTENT peripheral stent-graft manufactured by Jomed International AB, Stockholm, Sweden which includes a polytetrafluoroethylene covering internal to the structural portions of the stent-graft (see Journal of Endovascular Therapy 2000; 7: 136-140, 138).
While such known prior art stent-grafts are generally effective, they suffer from certain drawbacks. They are not all formed in a manner which provides a continuous layer of material. Rather, the covering is typically a woven fabric which can be susceptible to leakage, especially adjacent where sutures are utilized to hold the stent-graft in place. Additionally, they generally suffer from poor integration of the covering layer with the support structure, resulting in locations for restenosis and other corrosive material within the stent-graft which can lead to fluid disruption through the stent-graft.
They also are difficult to collapse and expand radially to a great extent. Accordingly, a need exists for a stent-graft which provides a smooth continuous inside surface and which can readily be positioned either intraluminally or with direct surgery at a site where a body lumen is damaged.
This invention provides a stent-graft which includes a smooth solid film providing an inside surface which is free of irregularities in texture and which is non-foraminous, rather than formed from a woven material with the intended gaps between threads or other porous material. This film can provide the tubular structure of the stent-graft alone or can be supported with various different support structures. The support structures can be metallic, such as a radially expandable stent structure or can be a woven support structure. In either case, the support structure is at least partially embedded within the film so that surface irregularities are not introduced by the inclusion of the support structure. The stent-graft can be a tubular structure with two ends or can have intersections therein so that multiple different arms of the tubular structure of the stent-graft can be joined together and can be utilized to treat body lumens which have junctions therein.
Ends of the stent-graft can be attached to adjacent body lumens in one or more of three main ways. First, the stent-graft can be radially expanded and be formed from a shape memory material which exerts sufficient outward radial pressure against the lumen wall to hold the stent-graft in place. Second, sutures or other surgical structure attachment structures, such as clips, staples and the like, can be utilized directly between the stent-graft structure adjacent the ends and the lumen wall adjacent the stent-graft. Third, a band and collar combination can be utilized where a collar is included near an end of the stent-graft which has a groove passing circumferentially around the collar and with a band which can mate with the collar and extend into the groove somewhat with the lumen wall between the band and the groove, so that the collar and band together form a coupling to securely hold the stent-graft to the lumen.
While various different materials can form the film and other portions of the stent-graft, a parylene material is preferred. Parylene can be deposited within a vacuum onto a mandrel having a shape similar to the interior surface of the stent-graft. Hence, the stent-graft can be formed merely by depositing the parylene material onto the mandrel and then later removal of the mandrel, such as by chemically dissolving the mandrel. Additional layers of parylene or other coatings can later be applied to the stent-graft to bond at least portions of a support structure to the stent-graft. The support structure provides radial expandability, enhanced strength and resistance to tearing for the stent-graft and is incorporated directly into the film of the stent-graft.
Accordingly, a primary object of the present invention is to provide a stent-graft which provides a smooth, continuous, non-foraminous inside surface which can be utilized to be surgically implanted adjacent a damaged lumen to support fluid flow through the lumen.
Another object of the present invention is to provide a stent-graft which can be implanted intraluminally and then be radially expanded at the desired location to support fluid flow at the desired location.
Another object of the present invention is to provide a stent-graft which can be implanted with direct surgical techniques to replace a damaged body lumen.
Another object of the present invention is to provide a stent-graft which includes both a film and a support structure embedded within the film but formed from a different material with at least inside surfaces of the support layer remaining smooth and with secure coupling of the support structure with the film.
Another object of the present invention is to provide a coupling system for coupling stent-grafts to body lumens in a secure fashion.
Another object of the present invention is to provide a stent-graft which can be implanted and held in place with sutures without risk of tearing of the stent-graft.
Another object of the present invention is to provide a stent-graft which is formed from bio-compatible materials.
Another object of the present invention is to provide a stent-graft which includes multiple different arms for use in treating a branch in a body lumen which is damaged.
Another object of the present invention is to provide a method for manufacturing a stent-graft which avoids any need for seams which provides a smooth inside surface and secure coupling of a support layer of the stent-graft with support structure within the stent-graft.